The present invention relates to a pneumatic tire and more particularly to a pneumatic tire improved in dry performance, particularly dry threshold performance, while maintaining the wet performance.
The term "dry performance" of a pneumatic tire is intended to mean the traction and driveability during travelling on a dry road surface. In particular, the term "dry threshold performance" is intended to mean the threshold cornering force caused during cornering which serves as a measure of the driveability of the tire. On the other hand, the term "wet performance" of a pneumatic tire is intended to mean the traction and driveability during travelling on a wet road surface. The wet performance is greatly influenced by the ability of main grooves and subgrooves provided on the tread surface of reject water.
It is believed that a lowering in the groove area occupied by the main grooves and subgrooves on the tread surface is useful for improving the dry performance of a pneumatic tire. However, the lowering in the percentage groove area brings about a problem with a lowering in the wet performance due to a lowering in the ability to reject water. For this reason, in the conventional pneumatic tire for passenger cars, the percentage groove area of the tread surface was limited to 30 to 40% for the purpose of offering a balance between the dry performance and the wet performance.
However, the dry performance of the conventional tire cannot cope with an improvement in the performance of the engine of a passenger car in recent years, which renders the dry threshold performance during cornering unsatisfactory.